Modern society has adopted, and is becoming reliant upon, wireless communication devices for various purposes, such as connecting users of the wireless communication devices with other users. Wireless communication devices can vary from battery powered handheld devices to stationary household and/or commercial devices utilizing an electrical network as a power source. Due to rapid development of the wireless communication devices, a number of areas capable of enabling entirely new types of communication applications have emerged.
Cellular networks facilitate communication over large geographic areas. These network technologies have commonly been divided by generations, starting in the late 1970 s to early 1980 s with first generation (1 G) analog cellular telephones that provided baseline voice communications, to modern digital cellular telephones. GSM is an example of a widely employed 2 G digital cellular network communicating in the 900 MHZ/1.8 GHZ bands in Europe and at 850 MHz and 1.9 GHZ in the United States. While long-range communication networks, like GSM, are a well-accepted means for transmitting and receiving data, due to cost, traffic and legislative concerns, these networks may not be appropriate for all data applications.
Short-range communication technologies provide communication solutions that avoid some of the problems seen in large cellular networks. Bluetooth™ is an example of a short-range wireless technology quickly gaining acceptance in the marketplace. In addition to Bluetooth™ other popular short-range communication technologies include Bluetooth™ Low Energy, IEEE 802.11 wireless local area network (WLAN), Wireless USB (WUSB), Ultra Wide-band (UWB), ZigBee (IEEE 802.15.4, IEEE 802.15.4 a), and ultra-high frequency radio frequency identification (UHF RFID) technologies. All of these wireless communication technologies have features and advantages that make them appropriate for various applications.
Wireless security has become an important aspect of the overall security for systems as large as computer networks and as small as keyless door locks. Wireless devices such as mobile laptops and fixed access points may be vulnerable to attack by remotely located, high-power transmitters or directive antennas that increase the received signal level beyond a minimum distance from the receiver. Security attacks may be attempted by remotely located transmitters using advanced predictive algorithms that allow shorter processing times and therefore longer propagation delays for the response signals. Wireless proximity detection for actuating a door lock is used in automobiles and office buildings equipped with wireless receivers that unlock the door when a valid key fob with a wireless transmitter is brought within range.
Proving the proximity of a wireless device may be an important consideration in granting it access to a wireless system. In secure distance estimation or bounding, a wireless prover device attempts to prove its distance from a wireless verifier device and the verifier device attempts to verify the location of the prover device.
Conventional methods for secure distance estimation or bounding in wireless systems are based on two principles: 1) received signal strength (RSS) based proximity detection and 2) round-trip-time (RTT) based proximity detection.
In RSS-based methods, the proximity is detected by assuming a certain threshold for the received signal strength that is assumed to only be exceeded if the radio frequency transmitter (the prover) is closer to the receiver (the verifier) than a maximum allowed distance. In RTT-based methods, the proximity is detected by measuring the time required for a prover device to respond to a wake-up signal transmitted by a verifier device. If a predetermined maximum time is exceeded, the prover device is assumed to be too far from the receiver.
RSS-based security methods may be vulnerable to attack by remotely located, high-power transmitters or directive antennas that increase the received signal level beyond a minimum distance from the receiver. The RTT-based security methods may be vulnerable to attack by remotely located transmitters using advanced predictive algorithms that allow shorter processing times and therefore longer propagation delays for the response signals.